This invention relates to machines and to industrial processes. More particularly, the invention concerns a machine and a process for placing and bonding an elastic member to a moving substrate web while the elastic member is in an un-stretched or relaxed state.
In the manufacture of infant diapers, adult incontinence garments and the like, it is frequently desirable to attach an elastic member to the remainder of the diaper or garment in order to secure the diaper or garment about the legs or waist of the user. Typically, these articles are manufactured by a high-speed process in which individual parts of the diaper or garment are affixed to a moving web of material by adhesive or ultrasonic bonding. U.S. Pat. Nos. 3,987,794; 3,990,450; 3,995,638; 3,995,640; and 4,014,338 to Schaar describe such infant diapers having an elasticized waist band.
One problem associated with this process relates to the attachment of the elastic member to the moving web. In prior art machines and processes in which the elastic member is bonded to the substrate web in the stretched condition, there is frequently a tendency for the stretched elastic member to pull away from the substrate web before the bonds become fully annealed. Attempts to solve this problem center around various schemes for attaching the elastic member to the substrate web in an un-stretched condition.
U.S. Pat. No. 4,240,866 and its divisional, U.S. Pat. No. 4,285,747 to Rega describe a process of manufacture whereby an elastic waist member is attached in an un-stretched state to a substrate web in the manufacture of infant diapers.
U.S. Pat. No. 4,337,771 to Pieniak, et al. describes an infant diaper with an elongated elastic strip secure to at least one margin of the diaper at a central portion of the margin, with a unitary, relatively inelastic reinforced region in a corner of the diaper.
U.S. Pat. No. 4,400,227 to Riemersma discloses a method of applying elasticized garment cuffs in a stretched condition to a substrate web.
In accordance with the present invention there is provided, in its principal embodiment, a machine for placing and bonding elastic members in an un-stretched state to a substrate web. The elastic members have first and second ends defining a first un-stretched length, first and second end regions respectively proximate the first and second ends, and the substrate web has a longitudinal axis and first and second edges defining a first width, with first and second side regions respectively proximate the first and second edges.
The machine comprises an apparatus for gathering the substrate web to a second width which is less than the first width, and holding the gathered substrate web at this second width while receiving the elastic member in an un-stretched state. The elastic member is received on the substrate web in such an orientation that its length is in a direction transverse to the longitudinal axis of the substrate web.
An apparatus of the machine then bonds the first and second end regions of the elastic member to the first and second edge regions of the substrate web while the substrate web is gathered and the elastic member is in an un-stretched state. The bonding of the two ends of the relaxed elastic member to the substrate web leaves the remainder of the length of the elastic member un-bonded to the substrate web.
The machine further provides an apparatus for stretching the bonded elastic member while simultaneously un-gathering the substrate web to its first width. An apparatus of the machine then bonds at least a portion of the remainder of the length of the elastic member to the substrate web while the elastic member is in the stretched state.
In an alternative embodiment, the present invention provides a process for placing and bonding elastic members in an un-stretched state to a substrate web. The elastic members have first and second ends and a first un-stretched length, with first and second end regions respectively proximate the first and second ends. The substrate web has a longitudinal axis or centerline, first and second side edges defining a first width, and first and second side edge regions respectively proximate the first and second side edges.
The process of the invention comprises the steps of first gathering the substrate web to a second width which is less than the first width, and holding the gathered substrate web at this second width. Next, an elastic member is placed in an un-stretched state on the substrate web with the length of the elastic member being transverse to the longitudinal axis of the substrate web.
In the next step, the first and second end regions of the elastic member are bonded respectively to the first and second side edge regions of the substrate web while the elastic member is in an un-stretched state, leaving the remainder of the length of the elastic member un-bonded to the substrate web.
Next, bonded elastic member is stretched, simultaneously un-gathering the substrate web to its first width. Finally, at least a portion of the remaining previously un-bonded length of the elastic member is bonded to the substrate web while the elastic member is in the stretched state.